Project Spec E30 – Part IV: Building a Roll Cage

Driver-side NASCAR-style door bars extend to the outer door skin for maximum clearance and driver protection. The upper and lower rails connect to the vertical front and main hoops.

The NASA Club Codes and Regulations dictate the materials, size and layout of a proper roll cage, so we won’t delve into the CCR specs on this subject. That would be a great research project for you to do on your own before you have a cage built. When you take a good look, you will find that within the CCR guidelines, there are options for you to consider when deciding on a cage design.

One option includes a prefabricated bolt-in cage system. They tend to lack a precise custom fit, but will do the job they are designed for. For the absolute budget-minded builder, this route is the most cost effective way to go, with the compromise that the fitment will not be ideal.

Driver-side NASCAR-style door bars extend to the outer door skin for maximum clearance and driver protection. The upper and lower rails connect to the vertical front and main hoops.

The “seventh point” in this cage is the reinforcement for the driver’s foot well. This protects the driver’s feet in a frontal collision. The E30’s front wheel can intrude into the passenger compartment if an impact is severe enough, injuring or trapping feet and ankles.The door latch release cable uses a coated cable to minimize wear and tear on the driver’s suit and the interior paint all the while allowing for an easy exit from the car in an emergency.

Welded cages are also structurally superior. For this particular build, we decided on a lightweight yet strong cage with some enhancements that benefit the E30 chassis and its driver. It’s going to cost more than it needs to, but we feel safety is an area where one should never skimp to save money. At the same time, it doesn’t need to be an extravagant cage, either. A cage design can have a focus on safety yet have some comfortably custom features and still be cost effective.

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Another option for you to consider is to build a rally-quality cage, which could be dropped from the boundaries of space and still survive. There’s nothing wrong with going that route if that’s what you want in your cage. Just consider that for every extra bar you add, you are adding weight to the car. One must consider the tradeoff of weight versus safety benefits, because at some point the extra bars in the cage only equal extra weight and not necessarily a safer nor stronger design.

The fact is, a Spec E30 is one of the slowest classes that competes in NASA. The max terminal velocity is roughly 130 mph on some of the fastest tracks that NASA races on. Even then, the weight of the cars, in addition to the original chassis design, allows these cars to require only a minimal cage to do its job effectively in a worst-case scenario. Thank you BMW!
One specific weak point of the E30 chassis that must be pointed out is that when there is a frontal impact, the front wheel and tire will push into the wheel well. This impact tends to move the wheel well rearward and inboard, which has been known to trap driver’s feet under the clutch and brake pedals, break ankles or both.

For this reason, we will use a standard six-point cage design, but also will include a seventh point in the driver’s footwell area to protect the driver’s feet in the event of a front-end collision. It doesn’t do anything to stiffen the chassis. It’s mainly a safety feature for the driver. Since we consider this a safety feature for the driver, we will not be installing the same bar on the passenger side of the car since we never intend on having a passenger in the car.

We used self-tapping screws to hold the sheet metal in place over the heater opening on the inside of the car on the firewall. This allowed me to remove them one at a time and drill out the holes to pop-rivet the panel in place in lieu of using Cleco pins to hold the panel.I used sealer on the heater hose opening on the firewall before screwing a blocking plate in place. The CCR stipulates no holes in the firewall.The heater hose opening is sealed and fastened and contoured to the shape of the firewall.By waiting to replace the sunroof panel until after the cage was built, the fabricator had an easier time accessing and welding the roof bars. We covered the opening with sheet metal using pop rivets to fasten it and sealant to keep it water and air tight.

Another option was the use of NASCAR-style doorbars on the driver’s side only. The passenger side will receive the standard X-brace because we never intend on having a passenger in the car. If you do plan to have a passenger, then you should consider the same safety features for your passenger as you would afford the driver. The added weight of the NASCAR style door bars is deemed well worth the additional weight considering the protection they offer the driver in the event of a left-side, T-bone impact. Although I said we were going for a lightweight cage design, we felt that the enhanced driver’s safety and the way the NASCAR bars allow for easier ingress and egress was a worthy compromise of safety and comfort for weight.

The cage builder cut out the rear bulkhead sheet metal to fit the cage to the rear shock towers. We simply tacked them back into place before the car went to paint.

Once we decided on the cage design, it was time to find a shop that could do the work we were looking for. Cage prices vary from region to region so shopping around is worth your time. Also, try to find some examples of their work if you can. That will give you an idea of what to expect when you get your car back. Bringing a car completely stripped of the interior and ready to begin the cage fabrication, like we did, will save you money, so it’s well worth it to strip the interior yourself. We shopped around and found a shop that we knew had done previous cages on many other racecars. We liked the quality of their work and the price fell right into our budget of $2,500.

Two weeks later we got the call to come pick it up. We’re pretty happy with what we got back from the cage builder. The only complaint was that I failed to inspect the passenger side X bar. I had asked for it to have a 3D shape to fit into the space of the passenger door where I had removed the inner door skin. It wasn’t the end of the world because the cage still came out great.

Now that the car is back, we can continue with prepping the car for paint. That means the sunroof opening was skinned with sheet metal, using sealant and pop rivets to keep moisture out and to secure the skin to the roof. I waited to skin the sunroof until after the cage was built because leaving the opening for the fabricator helps facilitate the cage-building process. He installed the roof bars close to the roof, and in the process he repositioned some of the sheet metal around the sunroof opening on the inside. Additionally, on the firewall some openings were sealed up the same way, using sheet metal and pop rivets.

Here’s a shot of some of the work the cage builder did on the rear of the cage. He tied the main hoop support bars to the rear shock towers. Good stuff!Since the rules now allow for it on coupes and sedans, we welded in the convertible reinforcement plates that tie the front frame rails to the strut towers.

Now that the door bars were installed, I could fabricate the cable to open the door from the inside. You want the cable to be in an area that isn’t going to be behind the door bars. This is key in setting up the cable, which is attached to the release lever and runs to a fixed point on the front of the door, allowing for simply pushing or pulling the cable to get the door open. It’s easy to build and adjust and the materials are super cheap. I laugh at how many racecar parts come from your local hardware store!

If I were to do anything differently, I would probably install the race seat in the car so that the cage can be built around it in the door bar area. We had to reposition the seat to make it fit right instead of just dropping the seat into the car. Again, a minor fitment issue, but when your goal is to make the first race of the season and the car is gone for two weeks at a time for the cage and two more weeks for paint, all these minor adjustments and fixes bite deeply into the time needed to finish the build!

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